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Another Wildfire Danger: Heart Attacks

Wildfire smoke may trigger a heart complication or stroke in vulnerable people, a new U.S. study suggests.

Looking at the impact of the widespread California wildfires of 2015, researchers found a spike in emergency department visits for heart attacks, strokes and other cardiovascular complications.

The risk was largely seen among adults aged 65 and older.

Within a day of exposure to dense smoke, their risk of an emergency department visit for a heart attack rose by 42 percent. Meanwhile, their odds of an abnormal heart rhythm were 24 percent higher on a day of exposure to dense smoke — and stayed higher for a few days afterward.

The findings make sense, according to the U.S. Environmental Protection Agency researchers.

Many studies have tied air pollution to short- and long-term effects on people’s cardiovascular health.

In fact, when it comes to air pollutants known as particulate matter, “the data are extraordinarily strong,” said Dr. Wayne Cascio, director of the EPA’s National Health and Environmental Effects Laboratory in Durham, N.C.

Particulate matter refers to extremely fine air pollutants that can be inhaled into the lungs — potentially aggravating existing heart or lung diseases, according to the EPA.

Wildfire smoke contains particulate matter and other pollutants, like ozone and carbon monoxide. Yet studies so far have come to conflicting conclusions as to whether wildfire smoke can boost people’s cardiovascular risks.

That’s “surprising,” Cascio said, but it may be because past studies generally focused on single wildfire episodes.

The new study, published online April 11 in the Journal of the American Heart Association, analyzed California’s 2015 wildfire season, when a series of fires swept across more than 800,000 acres.

The researchers focused on emergency department visits in the eight California “air basins” most affected by wildfire smoke. In all, there were over 376,000 emergency department trips for heart problems or stroke during the study period.

Overall, the investigators found, those visits were more likely to happen on days when dense smoke closed in, or the few days afterward — versus “no smoke” days.

The risks were mainly concentrated among adults older than 64. Besides the elevated risks of heart attack and abnormal heart rhythms, older adults were 22 percent more likely to suffer worsening heart failure in the days after dense smoke rolled in.

In addition, older adults were up to 25 percent more likely to have an ischemic stroke — the kind caused by a blood clot — within a few days of smoke exposure, the findings showed.

“This suggests the risk is not just on the day of smoke exposure,” said Dr. Karin Pacheco, of National Jewish Health, a Denver hospital that specializes in lung and heart diseases.

“The risk persists for a few days afterward,” she said.

That’s something to remember if your area is being evacuated due to wildfire, according to Pacheco.

“If you live in a place where they’re evacuating,” she said, “that’s partly because of [poor air quality]. It’s not only because your house might burn down.”

Cascio pointed to several reasons bad air can cause a heart attack or stroke in vulnerable people: Particulate matter may, for instance, set off inflammatory responses in the blood vessels that could rupture an artery-clogging “plaque” and lead to a heart attack.

The air pollutants can also reach receptors in the lungs that, in turn, send messages to the brain that activate the body’s “fight or flight” response, Cascio said. Among other things, fight-or-flight boosts heart rate and blood pressure.

In general, it’s wise to stay indoors with the air conditioning on — rather than windows open — when air quality is poor, according to Dr. Gerald Fletcher. He’s a cardiologist at the Mayo Clinic in Jacksonville, Fla., and a spokesman for the American Heart Association.

If your usual exercise routine involves being outside, he said, bring it inside on days with poor air quality.

And in general, Fletcher said, it’s wise to make sure you have any risk factors for heart trouble or stroke — like high blood pressure or cholesterol — under control.

People can keep track of their local air quality, Cascio said, by visiting the EPA website AirNow.gov.